Johannes Kepler

Johannes Kepler (27 December 1571-15 November 1630) was a German astronomer, astrologer, and mathematician. Born in Wurttemberg, he studied for the Lutheran ministry, but he refused to sign the Formula of Concord, alienating both Lutherans and Catholics. He had no refuge during the Thirty Years War as a result, and he decided to teach mathematics at a seminary in Graz, Austria. There, he taught astronomy, and he developed three ideas: all planets move about the sun, a radius vector joining any planet to the sun sweeps out equal areas in equal lengths of time, and the squares of the sidereal periods of planets are proportional to the cubes of their mean distances from the sun. He invented the Kepler telescope as well, a major discovery.